1. Field of the Invention
The present invention relates to an outline font brightness value correction technique for eliminating a look of blot or irregularity of brightness value associated with a grayscale display of an outline font character.
2. Description of the Related Art
A use of an outline font makes it possible to display a high quality character in a free size based on one piece of data when displaying a character in equipment having a display device such as a Liquid Crystal Display (LCD).
The outline font used to be mainly utilized for a computers with a high computing process capability because of a necessity of calculation of contour lines and/or that of painting over within the contour lines until the recent years witnessing a use of the outline font for a built-in type piece of equipment such as a portable phone thanks to an improved process capability thereof.
When using the outline font in a display of a portable phone or the like, a user feels unnaturalness such as “the contour is blotted” and “the brightness is uneven” if the brightness is in half tone in a grayscale display although a grayscale display makes it possible to smooth out raggedness of the contour of a character.
Conventional methods for avoiding a feel of a user such as “the contour is blotted” and “the brightness is uneven” in a grayscale of the contour lines of the outline font include one that pre-attaches correction data for a grayscale value to outline font character data as shown in FIG. 1, and one that adjusts a position of a contour line by a calculation when processing for a display as shown in FIG. 2.
FIG. 1 is a block diagram showing a configuration of a first conventional system. The characteristic of the first conventional system is to comprise correction data generation means 73 for reading and displaying pre-correction outline font data 71 in character image display means 72 and generating corrected data by carrying out a manual work of inputting the correction data for a part of the displayed pre-grayscale correction outline font in which a user feels “unnatural half tone” until the user feels “natural”, and provide outline font data 74 as a result of the correction data generated by the correction data generation means 73 being added. As such, the first conventional system shown in FIG. 1 is configured for a person in charge of a design (i.e., a font designer) to apply a correction of a grayscale value to uncorrected outline font character data, so as to make a natural half tone, thereby making an output character image as a very high quality.
The first conventional system, however, is configured for a person in charge of a design (i.e., a font designer) to apply a correction of a grayscale value to uncorrected outline font character data, so as to make a natural half tone, and add it to the font data, thereby making the output character image a very high quality, and therefore is faced with the problem of requiring a tremendous amount of time and cost because a font designer must carry out a manual work of generating correction data for grayscale values of the entirety of Japanese fonts counting several thousands.
FIG. 2 is a block diagram showing a configuration of a second conventional system. The second conventional system is characterized by comprising reading a contour line from pre-correction outline font data 81 by employing contour line readout means 82, adjusting (i.e., fitting or such) a position of the contour line by a calculation of contour line position calculation means 83 and drawing a figure based on the contour line that is adjusted for position, and painting it over, by employing contour line drawing & paint-over means 84, followed by displaying the character image in character image display means 85.
FIGS. 3A and 3B are diagrams exemplifying an image display by the configuration of the second conventional system as described above, with FIG. 3A showing the case of applying no correction anywhere including the right bottom side of the character “articles” (which is an English word for the Kanji character shown in the drawing) for the grayscale display of the contour line of the outline font and FIG. 3B showing the case of applying a correction by means of a fitting to pixels existing on the right bottom side of the character “articles” for the grayscale display of the contour line of the outline font. As such, the configuration of the second conventional system is capable of eliminating a look of unnaturalness in the grayscale display by changing a thickness ratio of the horizontal column to vertical column of a character image existing on the right bottom side on the character “articles” as a result of applying a correction (i.e., fitting). On the other hand, a balance of length between the right vertical column and left vertical column can no longer be maintained, resulting in becoming a character that cannot be regarded as good character quality in a viewpoint of the user. Yet overall, the display example shown in FIG. 3B is capable of preventing the grayscale display of the contour line of an outline font from giving a look of unnaturalness by applying a correction by means of a fitting as compared to the case of the display example shown in FIG. 3A.
The second conventional system, however, is configured to move a contour line (i.e., an outline) only by the movement amount obtained by a calculation and therefore is faced with the problem of resulting in carrying out a correction that degrades a character quality significantly such as losing the characteristic of an original font of an output character image, even if the blot and/or uneven brightness values thereof can be reduced.
Incidentally, there are two approaches in the method for adjusting the position of a contour line by a calculation for a display process according to the second conventional system shown in FIG. 2. A first approach disclosed in reference patent documents 1 and 2 uses a method for moving it to the closest grid (e.g., a border line of an actual pixel) for the entirety of the contour lines, so as not to display a half tone regarding the horizontal and vertical lines. The display example shown in FIG. 3B shows a character image display example by the method. Meanwhile, a second approach disclosed in reference patent documents 3 and 4 calculates a movement amount of a line position in consideration of a movement amount of another contour line included in a single character, followed by moving it to an optimal position, thereby maintaining a consistency of line width and removing an uneven grayscale.    Patent document 1: Laid-Open Japanese Patent Application Publication No. H08-255254    Patent document 2: Laid-Open Japanese Patent Application Publication No. H11-38960    Patent document 3: Laid-Open Japanese Patent Application Publication No. H08-272353    Patent document 4: Laid-Open Japanese Patent Application Publication No. 2000-137480